linux-kernel - Re: [PATCH v2] rust: add flags for shadow call stack sanitizer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CANiq72mCzRBW7_H5Q4VQF8PGRFwaKJzQwOe8LOP2NbStz4husg@mail.gmail.com>
Date: Tue, 5 Mar 2024 13:14:19 +0100
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Jamie Cunliffe <Jamie.Cunliffe@....com>, Sami Tolvanen <samitolvanen@...gle.com>, 
	Masahiro Yamada <masahiroy@...nel.org>, Nathan Chancellor <nathan@...nel.org>, 
	Nicolas Schier <nicolas@...sle.eu>, Ard Biesheuvel <ardb@...nel.org>, Marc Zyngier <maz@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, Mark Brown <broonie@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Kees Cook <keescook@...omium.org>, 
	Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
	Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...sung.com>, 
	Valentin Obst <kernel@...entinobst.de>, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v2] rust: add flags for shadow call stack sanitizer

On Tue, Mar 5, 2024 at 12:58 PM Alice Ryhl <aliceryhl@...gle.com> wrote:
>
> Add flags to support the shadow call stack sanitizer, both in the
> dynamic and non-dynamic modes.
>
> Right now, the compiler will emit the warning "unknown feature specified
> for `-Ctarget-feature`: `reserve-x18`". However, the compiler still
> passes it to the codegen backend, so the flag will work just fine. Once
> rustc starts recognizing the flag (or provides another way to enable the
> feature), it will stop emitting this warning. See [1] for the relevant
> issue.
>
> Currently, the compiler thinks that the aarch64-unknown-none target
> doesn't support -Zsanitizer=shadow-call-stack, so the build will fail if
> you enable shadow call stack in non-dynamic mode. However, I still think
> it is reasonable to add the flag now, as it will at least fail the build
> when using an invalid configuration, until the Rust compiler is fixed to
> list -Zsanitizer=shadow-call-stack as supported for the target. See [2]
> for the feature request to add this.
>
> I have tested this change with Rust Binder on an Android device using
> CONFIG_DYNAMIC_SCS. Without the -Ctarget-feature=+reserve-x18 flag, the
> phone crashes immediately on boot, and with the flag, the phone appears
> to work normally.
>
> This contains a TODO to add the -Zuse-sync-unwind=n flag. The flag
> defaults to n, so it isn't a problem today, but the flag is unstable, so
> the default could change in a future compiler release.
>
> Link: https://github.com/rust-lang/rust/issues/121970 [1]
> Link: https://github.com/rust-lang/rust/issues/121972 [2]
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
> ---
> This patch raises the question of whether we should change the Rust
> aarch64 support to use a custom target.json specification. If we do
> that, then we can fix both the warning for dynamic SCS and the
> build-failure for non-dynamic SCS without waiting for a new version of
> rustc with the mentioned issues fixed.

If the arm64 maintainers are OK with the warning being triggered in that case:

Acked-by: Miguel Ojeda <ojeda@...nel.org>

Otherwise partially reverting to the `target.json` approach sounds good too.

I added the `-Zuse-sync-unwind=n` to the list at
https://github.com/Rust-for-Linux/linux/issues/2. Given the default is
what we want, I have put it in the "Good to have" section.

Cheers,
Miguel